From 347b266f7899e7c3e62d4c190146b5acc3ba2fff Mon Sep 17 00:00:00 2001
From: Calvin Rien <calvin@darktable.com>
Date: Tue, 3 Oct 2023 19:23:41 -0700
Subject: [PATCH 1/2] Receive unregister callback when removing listener

---
 Runtime/ServiceLocator.cs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Runtime/ServiceLocator.cs b/Runtime/ServiceLocator.cs
index 25c07db..7a9c8fd 100644
--- a/Runtime/ServiceLocator.cs
+++ b/Runtime/ServiceLocator.cs
@@ -75,6 +75,7 @@ public static void AddServiceListener<T>(Action<T, bool> serviceCallback) where
                 return;
             }
 
+            // If the service is registered immediately notify the listener
             if (TryGetService<T>(out var service))
             {
                 serviceCallback.Invoke(service, true);
@@ -103,6 +104,13 @@ public static void RemoveServiceListener<T>(Action<T, bool> serviceCallback) whe
                 return;
             }
 
+            // If the service is registered immediately notify the listener
+            if (TryGetService<T>(out var service))
+            {
+                // behave as if the service unregistered.
+                callbackWrapper.Invoke(service, false);
+            }
+
             var type = typeof(T);
 
             if (k_Callbacks.ContainsKey(type))

From d3e6c6d224ec1283c02e321676dfd1499339bef2 Mon Sep 17 00:00:00 2001
From: Calvin Rien <calvin@darktable.com>
Date: Mon, 24 Jun 2024 17:03:30 -0700
Subject: [PATCH 2/2] Add a delegate to Add/Remove listener

make TryGetService public.
---
 Runtime/ServiceLocator.cs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Runtime/ServiceLocator.cs b/Runtime/ServiceLocator.cs
index 7a9c8fd..a3cd782 100644
--- a/Runtime/ServiceLocator.cs
+++ b/Runtime/ServiceLocator.cs
@@ -11,6 +11,7 @@ public interface IService { }
 
     public static class ServiceLocator
     {
+        public delegate void ServiceCallback<T>(T service, bool registered);
         private delegate void ServiceLocatorDelegate(IService service, bool registered);
 
         private static readonly Dictionary<Type, IService> k_Services = new();
@@ -55,7 +56,7 @@ public static bool Unregister<T>(T service) where T : class, IService
             return false;
         }
 
-        private static bool TryGetService<T>(out T result) where T : class, IService
+        public static bool TryGetService<T>(out T result) where T : class, IService
         {
             if (k_Services.TryGetValue(typeof(T), out var service))
             {
@@ -67,7 +68,7 @@ private static bool TryGetService<T>(out T result) where T : class, IService
             return false;
         }
 
-        public static void AddServiceListener<T>(Action<T, bool> serviceCallback) where T : class, IService
+        public static void AddServiceListener<T>(ServiceCallback<T> serviceCallback) where T : class, IService
         {
             if (k_RegisteredCallbacks.ContainsKey(serviceCallback))
             {
@@ -97,7 +98,7 @@ public static void AddServiceListener<T>(Action<T, bool> serviceCallback) where
             k_RegisteredCallbacks.Add(serviceCallback, callbackWrapper);
         }
 
-        public static void RemoveServiceListener<T>(Action<T, bool> serviceCallback) where T : class, IService
+        public static void RemoveServiceListener<T>(ServiceCallback<T> serviceCallback) where T : class, IService
         {
             if (!k_RegisteredCallbacks.TryGetValue(serviceCallback, out var callbackWrapper))
             {